1. Field of the Invention
The present invention relates to a tray locking apparatus which firmly locks a tray inserted in a disc drive and unlocks the tray when it is unloaded from the disc drive.
2. Description of the Related Art
In a typical disc drive which uses a disc as a recording medium, a tray loading the disc and carrying it into the drive is provided. That is, when a disc that is loaded on a tray is inserted into the drive, the disc is loaded at a loading position in the drive and a recording or reproducing operation is performed with respect to the disc in the drive. The tray must not be ejected from the drive due to an external impact during recording or reproduction. Thus, to prevent the above accident, a locking apparatus to lock the tray that is inserted in the drive is provided.
FIG. 1 shows the structure of a conventional tray locking apparatus which is disclosed in Japanese Patent Publication No. 2000-11513. As shown in the drawing, the conventional tray locking apparatus includes a locking pin 35 provided in a drive main body 13, a locking lever 50 installed at the lower surface of a tray 14 which is selectively locked by the locking pin 35, and a driving mechanism 60 to drive the locking lever 50.
The locking lever 50 includes an arm 51 having a hook portion 51a coupled to the locking pin 35 and rotatably installed at a rotation shaft 53 provided at the lower surface of the tray 14, and a lever 52 rotatably installed on the rotation shaft 53 to be coaxial with the arm 51. The arm 51 is elastically biased by a first spring 55 clockwise with respect to the lever 52. The lever 52 is elastically biased by a second spring 56 clockwise with respect to the tray 14. Thus, the locking lever 50 receives an elastic force to make the hook portion 51a coupled to the locking pin 35.
The driving mechanism 60 includes a plunger 63 supported by a yoke 62 such that one end of the plunger 63 is coupled to a coupling pin 52e of the lever 52, a permanent magnet 64 applying an attraction force to the other end of the plunger 63, and a coil 61 wound around the yoke 62 and applying an electromagnetic force to the plunger 63.
When the tray 14 having the above locking apparatus is inserted into the drive main body 13, the hook portion 51a of the arm 51 is pushed by the locking pin 35 and rotated counterclockwise, as shown in FIG. 2A. Then, the tray 14 continues to enter the drive main body 13 and is completely loaded at an installation position in the drive main body 13, as shown in FIG. 2B, the arm 51 is returned to the original position by the elastic force of the first spring 55 and the hook portion 51a is caught by the locking pin 35. Thus, since the hooking portion 51a is caught by the locking pin 35, the hooking portion 51a is prevented from being removed from the main body 13. Here, since current flows in the coil 61 so that an electromagnetic force is applied to the plunger 63 in the opposite direction to the attraction force of the permanent magnet 64, a state in which the two forces are offset is maintained.
When the tray 14 is drawn from the drive main body 13, the direction of the current flowing in the coil 61 is controlled such that the electromagnetic force is applied to the plunger 63 in the same direction as the attraction force by the permanent magnet 14. Then, the plunger 63, receiving the attraction force of the permanent magnet 64 and the electromagnet force formed by the current flowing in the coil 61, is moved toward the permanent magnet 64, as shown in FIG. 2C. Here, the plunger 63 pulls the coupling pin 52e and the locking lever 50 is rotated counterclockwise. Accordingly, the hook portion 51a is separated from the locking pin 35 and the tray 14 is smoothly drawn from the drive main body 13.
A push unit (not shown) to apply an elastic force to the tray 14 in a direction outside the drive main body 14 is typically installed in the drive main body 13. Thus, during unlocking, the push unit slightly pushes the tray 14 outside the drive main body 13. Then, a user can manually pull the tray 14 from the drive main body 13. When the tray 14 is drawn during unlocking, current is applied to the coil 61 of the driving mechanism 60 so that an electromagnetic force in the opposite direction to the attraction force of the permanent magnet 64 is applied to the plunger 63. Then, the two forces are offset and the plunger 63 is in a free state. Here, the locking lever 50 is returned to the original position by the elastic force of the first and second springs 55 and 56, as shown in FIG. 2D.
However, in the tray locking apparatus having the above structure, when a strong impact is applied to the disc drive from the outside, the hook portion 51a of the locking lever 50 is unlocked as the hook portion 51a, caught by the locking pin 35, is slightly moved counterclockwise. If the impact acts in a direction in which the tray 14 is pushed out of the drive main body 13 during unlocking, the tray 14 can be ejected from the drive main body 13 so that a stable recording and reproduction operation is not possible.
Also, to maintain a locking state in which the hook portion 51a of the locking lever 50 is coupled to the locking pin 35 in the above locking apparatus, since current is continuously applied to the coil 61 to generate the electromagnetic force to offset the attraction force by the permanent magnet 64, power consumption increases.